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JEE MainMathematicsToughITF

The number of solutions of the
equation
 tan⁡−1(4{x})+cot⁡−1(x+[x]))=π2\ \tan^{- 1}(4\{ x\}) + \cot^{- 1}(x + \lbrack x\rbrack)) = \frac{\pi}{2},
is (where denotes greatest integer function and fractional

part function)

Show answer and solution
∵4{x}=x+[x]…(1)\because 4\{ x\} = x + \lbrack x\rbrack\ldots(1)
Case-1 Let x=I

O=I+I⇒I=0O = I + I \Rightarrow I = 0
Case-2 Let
x=I+F,0<f<1x = I + F,0 < f < 1
Equation (1) becomes

4f=I+f+I4f = I + f + I
f=2I3∴I=1,f=23∴r=53f = \frac{2I}{3}\therefore I = 1,f = \frac{2}{3}\therefore r = \frac{5}{3}
∴\therefore two solutions

Source: Grass-G / M-17 Mathematics Paper 26 Nov Second.docx

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